How to achieve vapor or steam effect with smoke sim?
Result:



Basic setup:


Change Blender units to Metric.





Create Circle (Shift + A > Mesh > Circle) with 2cm Radius and Fill Type > Ngon.
Press Space and type in "Quick Smoke". Select it.
Position domain as in the picture: 


 


Change Light Paths > Volume to 2. It will allow light go trough smoke thus it could be white.




Smoke Domain:


Change Resolution to 64. Higher resolution = more details.
Behavior > Temp to 0.4. Smoke will rise higher.
Behavior > Vorticity to 4. Smoke will have more 'wrinkles'.
Check Smoke Adaptive Domain.
Check Smoke High Resolution and change Noise Method > Strenght to 1.




Material:

Use this node setup:



You can control smoke density by changing Multiply value.

Final thoughts and .blend file:

You can play with Resolution and/or Smoke High Resolution Divisions to get more detailed smoke. 

You should save your file and change Smoke Cache to OpenVDB > Float (half) it will speed up whole setup. 

To play animation hit ALT + A or first Bake it under Smoke Cache.

Note that I'm using HDRI for lighting, it is packed in .blend file.